Effects of intermittent theta burst stimulation add-on to dialectical behavioral therapy in borderline personality disorder: results of a randomized, sham-controlled pilot trial

Dialectical behavioral therapy (DBT) and repetitive transcranial magnetic stimulation (rTMS) are both effective in borderline personality disorder (BPD). We hypothesized that intermittent theta burst stimulation (iTBS), a modified rTMS protocol that provides unilateral stimulation to the left dorsolateral prefrontal cortex, would enhance the effects of DBT and reduce BPD-specific symptoms more than sham stimulation. We performed a single-blind, randomized, sham-controlled pilot study to evaluate iTBS as an add-on to 8-week DBT for BPD in routine inpatient treatment. A total of 53 BPD patients were randomly assigned to either iTBS (n = 25) or sham stimulation (n = 28) in weeks 4-8 of DBT; 40 patients were eligible for inclusion in the analyses according to pre-specified criteria (≥ 16 of 20 iTBS sessions). The primary endpoint was change on the 23-item Borderline Symptom List; secondary endpoints were changes in depressive symptoms and general level of functioning. A mixed model repeated measures analysis with a 2 × 2 factorial between-subjects design showed no significant effect of add-on iTBS treatment, but a distinct trend was observed in favor of iTBS (Cohen's d = 0.23 for group difference). We found a main effect of DBT with and without iTBS over time, indicating efficacy of 8 weeks' DBT (d = 0.89-1.12). iTBS may be beneficial as an add-on to DBT in the long term and warrants further evaluation in larger studies. Trial registration Registered at drks.de (no. DRKS00020413) on January 13, 2020.